Stethoscopes are widely relied upon for acoustic diagnosis in medicine, in particular, for the diagnosis of cardiovascular disease. Stethoscopes, however, have limited functionality, both in design and implementation. For example, the stethoscope itself may only transfer a small fraction of the acoustic signal available at the chest surface to the listener's ears and the stethoscope may filter the cardiac acoustic signal in the process. Electronic stethoscopes may provide gain to improve signal volume, but may still filter the acoustic signal.
Even if the cardiac acoustic signal is transferred faithfully by the stethoscope, proper interpretation of the acoustic signal may be difficult. In particular, with respect to auscultation of the heart, much of the signal energy in many heart sounds may be outside of the range of human hearing. This situation can be compounded by the degradation of the listener's hearing which can be associated with, for example, age and/or exposure to excessive noise. Auscultation relies on correctly determining which of the primary heart sounds correspond to the systolic phase of the heart and which sounds correspond to the diastolic phase of the heart. This is made more difficult when the systolic and diastolic intervals become more equal, such as typically occurs at elevated heart rates.
Learning auscultation is also difficult. Auscultation relies on detecting the correct sequence of brief events that occur close in time, a skill that is often difficult for human listeners. Additionally, diagnostic instructional manuals rely on subjective descriptions of heart sounds, which require practice to appreciate. Furthermore, the practice and teaching of the clinical skill of auscultation of the heart has declined among physicians, partly due to non-reimbursement policies of providers or insurers. Recent studies have concluded that physicians can reliably identify only a small number of standard heart sounds and murmurs. Consequently, serious heart murmurs in many patients may go undetected by physicians.
This decline in auscultation skills has both led to, and been brought about by, a greater reliance on echocardiography. The reliance on echocardiography has weakened the appreciation of auscultation, and the diminished appreciation of auscultation has led to a greater reliance on echocardiography. An improved auscultatory scanner with signal processing capabilities, which is easily used, could greatly assist physicians in the screening process, thereby reducing the number of unnecessary echocardiograms administered.
An additional benefit of the auscultatory scanner would be to recover and re-establish an appreciation of the clinical value of auscultation of the heart, and to provide immediate feedback to the user that would help confirm and refine auscultatory skill, as well as provide a tool that would improve the diagnostic referral process, both in detecting latent murmurs and in correctly deciding not to refer asymptomatic patients with innocent murmurs and no additional associated findings.